沙雷氏菌(Serratia sp.) AXJ-M响应高温胁迫的生理适应性

Physiological adaptation of Serratia sp. AXJ-M to high temperature stress

摘要:

【背景】利用微生物法治理造纸废水或被其污染的环境具有重要的现实意义，但是关于微生物在造纸废水高温环境胁迫下的生理补偿适应机制尚缺乏探讨。【目的】以实验室保藏的一株嗜热木质素降解菌Serratia sp. AXJ-M为对象，开展其对热胁迫的生理响应机制研究。【方法】设计温度胁迫培养实验，采集不同温度下的菌体，测定菌体形态、细胞膜流动性与渗透性、细胞海藻糖含量及抗氧化酶的活性变化。基于Illumina Hiseq 2000平台对菌株AXJ-M进行de novo测序分析，用gene ontology (GO)、clusters of orthologous groups of proteins (COG)、Kyoto encyclopedia of genes and genomes (KEGG)及non-redundant database (NR)进行基因组基本功能注释。【结果】热胁迫实验表明，菌株AXJ-M能够在50−80 ℃的热胁迫环境中生存，其中50 ℃是最适生长温度，在高于70 ℃的热胁迫环境下其生长会被明显抑制。相较于最适温度(50 ℃)，菌株AXJ-M经热胁迫培养后细胞表面粗糙程度增加、细胞膜流动性降低、膜通透性提高、海藻糖含量提高。高温胁迫(80 ℃)下与氧化应激有关的一些酶活性显著增加，过氧化氢酶(catalase, CAT)、超氧化物歧化酶(superoxide dismutase, SOD)和过氧化物酶(peroxidase, POD)活性随着培养时间的延长分别提高50%‒80%、30%‒47%、24%‒31%。将基因组测序结果与数据库比对并检索，菌株AXJ-M含有参与响应热胁迫的相关基因。【结论】热胁迫培养可诱导菌株AXJ-M产生耐热性并使菌体形态发生改变，海藻糖含量和抗氧化酶活性的升高保护细胞抵抗外界不良环境。菌株全基因组的初步解析，对研究嗜热菌在高温环境中的分子反应机制奠定了基础。

Abstract:

[Background] The microbial treatment of paper wastewater or the polluted environment is of great practical value. However, studies remain to be carried out regarding the physiological adaption mechanisms of microorganisms to the high temperatures of paper wastewater. [Objective] To investigate the physiological response of Serratia sp. AXJ-M, a thermophilic lignin-degrading bacterial strain preserved in our laboratory, to high temperature stress. [Methods] The bacterial cells were cultured at different temperatures, and the bacterial cell morphology, cell membrane fluidity and permeability, trehalose content, and activities of antioxidant enzymes were observed and measured. Illumina HiSeq 2000 was used for the de novo sequencing of AXJ-M, and then GO, COG, KEGG, and NR were employed to annotate the functional genes in the genome. [Results] Strain AXJ-M can survive in a thermal stress environment of 50 to 80 ℃, of which 50 ℃ is the optimal growth temperature. However, its growth was significantly hindered when the temperature was rises above 70 ℃. Strain AXJ-M exhibited marked morphological differences and augmented surface roughness at high temperature stress. Strain AXJ-M cultured at 80 ℃ experienced a decline in cell membrane fluidity, an upsurge in membrane permeability, and a rise in trehalose content. Moreover, the activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) associated with oxidative stress increased by 50%–80%, 30%–47%, and 24%–31%, respectively, as the culture time was extended. By genomic analysis, strain AXJ-M contained the genes associated with the response to high temperature stress. [Conclusion] The culture at high temperatures can induce strain AXJ-M to develop heat tolerance and modify the cell morphology. Additionally, the increased trehalose content and antioxidant enzyme activities can protect the cells from external stress conditions. Moreover, a comprehensive analysis of the strain genome provides a basis for exploring the molecular response mechanism of thermophilic bacteria in high-temperature environments.